Why can't anyone kill me :(

Cool story bro time. I loaded up an old lv 81 character I had ignored the other day - last time I played was before Dawnguard was released. I traveled to Whiterun and suddenly the following characters all appeared before Warmaidens:

Total carnage broke out. The vampires and death hounds began attacking everyone. The Ebony Warrior began attacking the vampires. The vampires began raising dead townsfolk and in the middle of this the Cultists are too busy trying to ask me if I'm Dragonborn. I decided to retreat to a safe distance and watch the fun.

Something went wrong and a guard must have struck the Ebony Warrior by accident, as after he killed the vampires and culitist he went batshit and began killing everything in sight. Guards were falling in three or four hits and regular townsfolk didn't even stand a chance, even poor Nazeem. Durak chickened out and was nowhere to be seen.

Bodies everywhere.  I think most of the town was killed. Certainly no guards left.

I lured him to Jorrvaskr hoping to provoke the wrath of the Companions. Weaklings - all of them. Despite being essential and hence immortal, Farkas, Vilkas, Skjor and Aela couldn't even dent his health bar and were falling to their knees constantly. Ysgramor would have been spinning in his barrow.

And that is why Skyrim is awesome.